Castle Romeo

Castle Romeo
Castle Romeo mushroom cloud.
Information
Country	United States
Test series	Operation Castle
Test site	Bikini Atoll
Date	March 27, 1954
Test type	Atmospheric
Yield	11 Mt

Castle Romeo was the code name given to one of the tests in the Operation Castle series of American nuclear tests. It was the first test of the TX-17 thermonuclear weapon (initially the "emergency capability" EC-17), the first deployed thermonuclear bomb.

The so-called "runt" device was a weaponized "dry" fusion bomb, using lithium deuteride fuel for the fusion stage of a "staged" fusion bomb, unlike the cryogenic liquid deuterium of the first-generation Ivy Mike fusion device.

Similar to the "Shrimp" device tested shortly before, in the Castle Bravo test, it differed from that device in using lithium deuteride derived from natural lithium (a mixture of lithium-6 and lithium-7 isotopes, with 7.5% of the former) as the source of the tritium and deuterium fusion fuels, as opposed to the relative high enrichment level of lithium (approximately 40% lithium-6) deuteride used in Bravo.

It was detonated on March 27, 1954, after several delays (which played havoc with the planned experimental measurements program) at Bikini Atoll of the Marshall Islands, on a barge moored in the middle of the crater from the Castle Bravo test. It was the first such barge-based test, a necessity that had come about because the powerful thermonuclear devices completely obliterated the small islands following detonation.

Like the Bravo test, it "ran away" and produced far more than its predicted yield, and for the same reason—an unexpected participation of the common lithium-7 isotope in fusion reactions. Although it had been predicted to produce a yield of 4 megatons with a range of 1.5 to 7 megatons (before the results of the Bravo test caused an upgrade in the estimates, it had originally been estimated to produce 3–5 megatons), it actually produced a yield of 11 megatons, the third-largest test ever conducted by the U.S.